1. Field of the Invention
The present invention relates to on the ground aircraft de-icers and methods, and more particularly relates to a de-icer having a proportional mix system for applying a thixotropic de-icing fluid and hot water during de-icing to the aircraft surfaces and for applying the thixotropic fluid to the surfaces during anti-icing with a minimum loss of viscosity due to pumping and overheating of the thixotropic fluid.
2. Description of the Prior Art
The use of thixotropic de-icing fluids in an aircraft de-icer is known in the art. British Pat. No. 822,811 which was published on Nov. 4, 1959 discloses an aircraft de-icer that includes a de-icing fluid tank for a hot dilute glycol and water mixture used for de-icing, and another tank for a supply of hot concentrated de-icing fluid for anti-icing the aircraft. The patentee specifies the use of a Kilfrost de-icing jelly or other forms of de-icing fluids. The patentee, however, heats the de-icing fluid in both tanks, and also provides an agitating pump for circulating the water de-icing fluid mixture in the large tank. A single pump and certain control valves are used for spraying both the hot water/de-icing fluid mixture, and the hot concentrated anti-icing fluid onto the aircraft during the de-icing and anti-icing treatments.
German Pat. No. 1,266,139 which issued to SchulzeEckel on Apr. 11, 1968 covers a proportioning valve for an aircraft de-icer which may be adjusted during operation to provide a water and de-icing fluid mixture having anywhere between zero to one-hundred percent glycol. The de-icing mixture includes any commercial de-icing fluid of different viscosities, and such fluids are used either when hot or cold but preferably when heated. The apparatus includes a water tank and a glycol tank with either one or two piston pumps which lead from their supply tanks to a mixing tank adjacent one or more spray nozzles. The strokes of the piston pumps are said to be adjustable individually between zero and one-hundred percent during operation.
U.S. Pat. No. 4,032,090 which issued to Thornton-Trump on June 28, 1977 discloses a method of using hot water alone, or using a mixture of hot water and glycol, depending on the atmospheric conditions, for de-icing an aircraft. The de-icing liquid solution is heated to about 160.degree. F. to 190.degree. F., and when glycol is used in the de-icing fluid, its maximum percentage is up to only about ten percent glycol. When anti-icing is required, the percentage of glycol in water is up to about thirty percent.
U.S. Thronton-Trump Pat. No. 4,073,437 which issued on Feb. 14, 1978 discloses a conversion unit that is secured to the rear end of an aircraft de-icer. The patent discloses a water tank, a water pump on the de-icer, and a nozzle on the de-icer all of which communicate with a heater on the conversion unit through a first water conduit. A glycol tank, proportioning valve, and the nozzle on the de-icer communicates with a glycol pump on the conversion unit by a second or glycol conduit. The conversion unit permits the de-icer to direct hot water alone or a hot water-glycol mix onto an aircraft depending upon the setting of the proportioning valve. When the de-icing/anti-icing operations are completed, the water lines and water pump are purged through a purge line which communicates with the glycol conduit near the suction side of the pump and with the water conduit between the water pump and water tank.
Assignee's U.S. Pat. No. 3,243,123 which issued to Inghram et al on Mar. 29, 1966 discloses a conventional de-icer with several pumps and fluid supply tanks.